Metal film and method for forming same

Abstract

To provide a metal film excellent in wear resistance and adhesion, and a method for depositing the same.SOLUTION: A metal film 5 formed on a surface of a base material 4 includes a soft material 51 and a hard material 52 as a main component. The weight ratio of the hard material included in the film to the soft material is different in a thickness direction and / or an extension direction of the film, and the weight ratio of the soft material 51 included in a film portion 53 close to the base material 4 in the thickness direction of the film to the hard material 52 is larger than that of the soft material 51 included in a film portion 54 distant from the base material 4 in the thickness direction of the film to the hard material 52.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a metal film and a method for forming the same, and more particularly to a metal film formed by a cold spray method and a method for forming the film by the cold spray method. [Background technology]

[0002] A method for manufacturing a sliding member is known in which a valve seat having excellent high-temperature abrasion resistance is formed by spraying a raw material powder of metal or the like onto the seating portion of an engine valve by a cold spray method (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 022505 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] The valve seats of this type of engine are required to have wear resistance against repeated impacts of the intake and exhaust valves, and to have good adhesion to the substrate. To improve the wear resistance of the valve seats, a hard material can be used for the raw powder of the cold spray, but a hard material is difficult to plastically deform, and the adhesion to the substrate decreases. Conversely, to improve the adhesion of the valve seats, a soft material can be used for the raw powder of the cold spray, but this reduces wear resistance. Thus, there is a trade-off between wear resistance and adhesion in the cold spray method, and it has been difficult to achieve both.

[0005] An object of the present invention is to provide a metal film having both excellent wear resistance and adhesion, and a method for forming the same. [Means for solving the problem]

[0006] The present invention solves the above problem by forming a metal film on the surface of a substrate using a cold spray method with a raw material powder containing a soft material and a hard material as main components, such that the weight ratio of the hard material to the soft material contained in the film varies depending on the thickness direction and / or the extension direction of the film. Effect of the Invention

[0007] According to the present invention, a metal film having excellent wear resistance and adhesion can be obtained by making the film portion close to the substrate rich in soft material and making the film portion far from the substrate rich in hard material. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a cylinder head including a valve seat film to which a metal film and a film forming method thereof according to the present invention are applied; [Diagram 2] FIG. 2 is an enlarged cross-sectional view of the periphery of the valve in FIG. 1. [Diagram 3] 1 is a configuration diagram showing an embodiment of a cold spray device used in a film formation method according to the present invention. [Figure 4] 1A to 1C are process diagrams showing a procedure for manufacturing a cylinder head using a film forming method according to the present invention. [Diagram 5] 1 is a perspective view of a cylinder head blank including a valve seat film to which the metal film and the film forming method according to the present invention are applied; FIG. [Figure 6A] 6 is a cross-sectional view showing the intake port taken along line VI-VI in FIG. 5. [Figure 6B] 6B is a cross-sectional view showing the intake port of FIG. 6A after an annular valve seat portion has been formed in a cutting process. FIG. [Figure 6C] FIG. 6C is a cross-sectional view showing a state in which a valve seat film is formed in the intake port of FIG. 6B. [Figure 6D] FIG. 4 is a cross-sectional view showing an intake port on which a valve seat film is formed. [Figure 6E] FIG. 5 is a cross-sectional view showing the intake port after the finishing process of FIG. 4. [Figure 7]1 is a graph showing the relationship between the wear resistance and adhesion versus the weight ratio of a hard material contained in a film. [Figure 8] 1 is a cross-sectional view showing a valve seat film of an embodiment of a metal film according to the present invention. [Figure 9A] 9A to 9C are plan views (part 1) illustrating a procedure for forming the valve seat film in FIG. 8. [Figure 9B] 9A to 9C are plan views (part 2) illustrating a procedure for forming the valve seat film in FIG. 8. [Figure 10A] 11A and 11B are schematic diagrams showing a film formation state when the nozzle moving speed is low. [Figure 10B] 11A and 11B are schematic diagrams showing a film formation state when the nozzle moving speed is high. [Figure 11] FIG. 11 is a configuration diagram showing another embodiment of a cold spray device used in the film forming method according to the present invention. [Figure 12] FIG. 12 is a side view showing a film formation method using the cold spray apparatus of FIG. [Figure 13A] 5A and 5B are a cross-sectional view showing a valve seat film of another embodiment of the metal film according to the present invention and a graph showing the component ratios. [Figure 13B] 13 is a cross-sectional view showing a valve seat film of still another embodiment of the metal film according to the present invention, and a graph showing the component ratios. [Figure 13C] 13 is a cross-sectional view showing a valve seat film of still another embodiment of the metal film according to the present invention, and a graph showing the component ratios. [Figure 14] FIG. 11 is a plan view showing a valve seat film of still another embodiment of the metal film according to the present invention. [Figure 15] FIG. 11 is a configuration diagram showing still another embodiment of a cold spray device used in the film forming method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the present invention will be described below with reference to the drawings. First, an internal combustion engine 1 equipped with a valve seat film to which the metal film and the film forming method according to the present invention are preferably applied will be described. Fig. 1 is a cross-sectional view of the internal combustion engine 1, and mainly shows the configuration around the cylinder head.

[0010] The internal combustion engine 1 includes a cylinder block 11 and a cylinder head 12 attached to the top of the cylinder block 11. The internal combustion engine 1 is, for example, an in-line four-cylinder gasoline engine, and the cylinder block 11 has four cylinders 11a arranged in the depth direction of the drawing. Each cylinder 11a houses a piston 13 that reciprocates up and down in the drawing, and each piston 13 is connected to a crankshaft 14 extending in the depth direction of the drawing via a connecting rod 13a.

[0011] Four recesses 12b constituting the combustion chamber 15 of each cylinder are formed in the mounting surface 12a of the cylinder head 12 to the cylinder block 11 at positions corresponding to each cylinder 11a. The combustion chamber 15 is a space for burning a mixture of fuel and intake air, and is composed of the recesses 12b of the cylinder head 12, the top surface 13b of the piston 13, and the inner circumferential surface of the cylinder 11a.

[0012] The cylinder head 12 includes an intake port 16 that communicates the combustion chamber 15 with one side surface 12c of the cylinder head 12. The intake port 16 has a curved, generally cylindrical shape, and guides intake air from an intake manifold (not shown) connected to the side surface 12c into the combustion chamber 15. The cylinder head 12 also includes an exhaust port 17 that communicates the combustion chamber 15 with the other side surface 12d of the cylinder head 12. The exhaust port 17 has a curved, generally cylindrical shape like the intake port 16, and discharges exhaust gas generated in the combustion chamber 15 to an exhaust manifold (not shown) connected to the side surface 12d. The internal combustion engine 1 of this embodiment includes two intake ports 16 and two exhaust ports 17 for each cylinder 11a.

[0013] The cylinder head 12 includes an intake valve 18 that opens and closes an intake port 16 relative to the combustion chamber 15, and an exhaust valve 19 that opens and closes an exhaust port 17 relative to the combustion chamber 15. The intake valve 18 and the exhaust valve 19 include round rod-shaped valve stems 18a and 19a, respectively, and disk-shaped valve heads 18b and 19b provided at the tips of the valve stems 18a and 19a. The valve stems 18a and 19a are slidably inserted into approximately cylindrical valve guides 18c and 19c assembled to the cylinder head 12. This allows the intake valve 18 and the exhaust valve 19 to move relative to the combustion chamber 15 along the axial direction of the valve stems 18a and 19a, respectively.

[0014] 2 shows an enlarged view of the communication portion between the combustion chamber 15 and the intake port 16 and exhaust port 17. The intake port 16 has a substantially circular opening 16a at the communication portion with the combustion chamber 15. An annular valve seat membrane 16b that abuts against a valve head 18b of the intake valve 18 is formed on the annular edge portion (valve seat portion) of this opening 16a. When the intake valve 18 moves upward along the axial direction of the valve stem 18a, the upper surface of the valve head 18b abuts against the valve seat membrane 16b to close the intake port 16. Conversely, when the intake valve 18 moves downward along the axial direction of the valve stem 18a, a gap is formed between the upper surface of the valve head 18b and the valve seat membrane 16b to open the intake port 16.

[0015] The exhaust port 17 has a substantially circular opening 17a at the communicating portion with the combustion chamber 15, similar to the intake port 16, and an annular valve seat membrane 17b that abuts against a valve head 19b of the exhaust valve 19 is formed on the annular edge (valve seat) of the opening 17a. When the exhaust valve 19 moves upward along the axial direction of the valve stem 19a, the upper surface of the valve head 19b abuts against the valve seat membrane 17b to close the exhaust port 17. Conversely, when the exhaust valve 19 moves downward along the axial direction of the valve stem 19a, a gap is formed between the upper surface of the valve head 19b and the valve seat membrane 17b to open the exhaust port 17. The diameter of the opening 16a of the intake port 16 is set to be larger than the diameter of the opening 17a of the exhaust port 17.

[0016] In the four-stroke internal combustion engine 1, when the piston 13 descends, only the intake valve 18 is opened, thereby introducing the air-fuel mixture from the intake port 16 into the cylinder 11a (intake stroke). Next, the intake valve 18 and exhaust valve 19 are closed, and the piston 13 is raised to approximately the top dead center to compress the air-fuel mixture in the cylinder 11a (compression stroke). Then, when the piston 13 reaches approximately the top dead center, the compressed air-fuel mixture is ignited by an ignition plug, causing the mixture to explode. This explosion causes the piston 13 to descend to the bottom dead center, and the explosion is converted into rotational force via the connected crankshaft 14 (combustion and expansion stroke). Finally, when the piston 13 reaches the bottom dead center and starts to rise again, only the exhaust valve 19 is opened, and the exhaust gas in the cylinder 11a is discharged to the exhaust port 17 (exhaust stroke). The internal combustion engine 1 generates power by repeating the above cycle.

[0017] The valve seat films 16b, 17b are formed directly on the annular edges of the openings 16a, 17a of the cylinder head 12, i.e., the valve seating portions, by the cold spray method. In the cold spray method, a working gas at a temperature lower than the melting point or softening point of the raw material powder is made into a supersonic flow, and the raw material powder carried by a carrier gas is injected into the working gas and sprayed from the nozzle tip, and the raw material powder is made to collide with a substrate in a solid phase state, forming a coating by plastic deformation of the raw material powder. Compared with the thermal spray method in which the material is melted and attached to the substrate, the cold spray method has the following characteristics: a dense coating that does not oxidize in the atmosphere is obtained, thermal deterioration is suppressed because the thermal effect on the material particles is small, the coating speed is fast, a thick coating can be formed, and the deposition efficiency is high. In particular, since the coating speed is fast and a thick coating can be formed, the cold spray method is suitable for use as a structural material such as the valve seat films 16b, 17b of the internal combustion engine 1.

[0018] 3 is a schematic diagram of the cold spray device 2 used to form the above-mentioned valve seat films 16b and 17b. The cold spray device 2 of this example includes a gas supply unit 21 for supplying a working gas and a carrier gas, a raw material powder supply unit 22 for supplying raw material powder for the valve seat films 16b and 17b, a spray gun 23 for spraying the raw material powder as a supersonic flow using a working gas at or below its melting point, and a refrigerant circulation circuit 27 for cooling the nozzle 23d.

[0019] The gas supply unit 21 includes a compressed gas cylinder 21a, a working gas line 21b, and a carrier gas line 21c. The working gas line 21b and the carrier gas line 21c include a pressure regulator 21d, a flow control valve 21e, a flow meter 21f, and a pressure gauge 21g, respectively. The pressure regulator 21d, the flow control valve 21e, the flow meter 21f, and the pressure gauge 21g are used to adjust the pressure and flow rate of the working gas and the carrier gas from the compressed gas cylinder 21a.

[0020] A heater 21i such as a tape heater is installed in the working gas line 21b, and the heater 21i heats the working gas line 21b by receiving power from a power source 21h via power supply lines 21j, 21j. The working gas is heated by the heater 21i to a temperature lower than the melting point or softening point of the raw material powder, and then introduced into the chamber 23a of the spray gun 23. A pressure gauge 23b and a thermometer 23c are installed in the chamber 23a, and the detected pressure and temperature values ​​are output to a controller (not shown) via signal lines 23g, 23h, respectively, for feedback control of the pressure and temperature.

[0021] Meanwhile, the raw material powder supplying section 22 includes a raw material powder supplying device 22a, a measuring device 22b and a raw material powder supplying line 22c attached thereto. Carrier gas from a compressed gas cylinder 21a passes through the carrier gas line 21c and is introduced into the raw material powder supplying device 22a. A predetermined amount of raw material powder measured by the measuring device 22b is conveyed into the chamber 23a through the raw material powder supplying line 22c.

[0022] The spray gun 23 sprays the raw material powder P, which has been carried into the chamber 23a by the carrier gas, from the tip of the nozzle 23d as a supersonic flow by the working gas, and causes it to collide with the substrate 4 in a solid phase state or a solid-liquid coexistence state to form a metal film 5. In this embodiment, a cylinder head 12 is used as the substrate 4, and the raw material powder P is sprayed onto the annular edges of the openings 16a, 17a of the cylinder head 12 by a cold spray method, thereby forming valve seat films 16b, 17b as the metal films 5.

[0023] Nozzle 23d has a flow path (not shown) through which a coolant such as water flows. Nozzle 23d has coolant inlet 23e at its tip for introducing the coolant into the flow path, and coolant outlet 23f at its base end for discharging the coolant in the flow path. Nozzle 23d cools nozzle 23d by introducing the coolant from coolant inlet 23e into the flow path, flowing the coolant in the flow path, and discharging the coolant from coolant outlet 23f.

[0024] The refrigerant circulation circuit 27 that circulates the refrigerant through the flow path of the nozzle 23d includes a tank 271 that stores the refrigerant, an inlet pipe 274 connected to the above-mentioned refrigerant inlet portion 23e, a pump 272 that is connected to the inlet pipe 274 and flows the refrigerant between the tank 271 and the nozzle 23d, a cooler 273 that cools the refrigerant, and a discharge pipe 275 that is connected to the refrigerant discharge portion 23f. The cooler 273 is, for example, a heat exchanger, and cools the refrigerant whose temperature has increased by cooling the nozzle 23d by exchanging heat with a refrigerant such as air, water, or gas.

[0025] The refrigerant circulation circuit 27 sucks the refrigerant stored in the tank 271 by the pump 272, and supplies the refrigerant to the refrigerant introduction part 23e via the cooler 273. The refrigerant supplied to the refrigerant introduction part 23e flows through the flow path in the nozzle 23d from the front end side to the rear end side, and cools the nozzle 23d by exchanging heat with the nozzle 23d during that time. The refrigerant that has flowed to the rear end side of the flow path is discharged from the refrigerant discharge part 23f to the discharge pipe 275 and returns to the tank 271. In this way, the refrigerant circulation circuit 27 circulates the refrigerant while cooling it to cool the nozzle 23d, so that adhesion of the raw material powder P to the injection passage of the nozzle 23d can be suppressed. The raw material powder P will be described later.

[0026] In the cold spray device 2 of this embodiment, the cylinder head 12 on which the valve seat films 16b, 17b are formed is fixed to a base 45, while the tip of the nozzle 23d of the spray gun 23 is rotated along the annular edge of the openings 16a, 17a of the cylinder head 12 to spray the raw material powder. Since the cylinder head 12 is not rotated, a large occupied space is not required, and the spray gun 23 has a smaller moment of inertia than the cylinder head 12, so that it has excellent rotation transient characteristics and responsiveness. However, since the metal film and the film forming method thereof of the present invention only require the cylinder head 12, which is the base material, and the nozzle 23d to move relatively, the nozzle 23d of the spray gun 23 may be fixed while the cylinder head 12 is rotated and oscillated, or the cylinder head 12 may be rotated and oscillated together with the nozzle 23d of the spray gun 23.

[0027] Next, a method for manufacturing the cylinder head 12 having the valve seat membranes 16b, 17b will be described. Fig. 4 is a process diagram showing the machining process of the valve parts in the manufacturing method of the cylinder head 12 of this embodiment. As shown in the figure, the manufacturing method of the cylinder head 12 of this embodiment includes a casting process S1, a cutting process S2, a coating process S3, and a finishing process S4. Note that the machining processes other than those for the valve parts are omitted for the sake of simplicity of explanation.

[0028] In the casting process S1, aluminum alloy for casting is poured into a metal mold in which a sand core is set, and a cylinder head blank 3 having an intake port 16, an exhaust port 17, etc. formed in the main body is cast. Here, the cylinder head blank 3 refers to a semi-finished product in the middle of manufacturing before being processed into a cylinder head 12 as a final product. The intake port 16 and the exhaust port 17 are formed by the sand core, and the recesses 12b are formed by the metal mold. FIG. 5 is a perspective view of the cylinder head blank 3 cast in the casting process S1, seen from the mounting surface 12a side to the cylinder block 11. The cylinder head blank 3 has four recesses 12b, and two intake ports 16 and two exhaust ports 17 provided in each recess 12b. The two intake ports 16 and two exhaust ports 17 of each recess 12b are gathered into one in the cylinder head blank 3, and are connected to openings provided on both sides of the cylinder head blank 3, respectively.

[0029] 6A is a cross-sectional view of the cylinder head blank 3 taken along line VI-VI in FIG. 5, and shows the intake port 16. The intake port 16 is provided with a circular opening 16a exposed in the recess 12b of the cylinder head blank 3.

[0030] In the next cutting step S2, the cylinder head blank 3 is milled using an end mill, a ball end mill, or the like, to form an annular valve seat portion 16c at the opening 16a of the intake port 16, as shown in FIG. 6B. FIG. 6B is a cross-sectional view showing the state in which the annular valve seat portion is formed in the cutting step on the intake port of FIG. 6A. The annular valve seat portion 16c is an annular groove that serves as the base shape of the valve seat film 16b, and is formed on the outer periphery of the opening 16a. In the manufacturing method of the cylinder head 12 of this embodiment, the raw material powder P is sprayed on the annular valve seat portion 16c by the cold spray method to form a film, and the film is used as the base to process into the valve seat film 16b. Therefore, the annular valve seat portion 16c is formed to be one size larger than the valve seat film 16b.

[0031] In the coating step S3, the raw material powder P is sprayed onto the annular valve seat portion 16c of the cylinder head blank 3 using the cold spray device 2 of this embodiment to form a valve seat film 16b. More specifically, in this coating step S3, as shown in Fig. 6C, while the annular valve seat portion 16c and the nozzle 23d of the spray gun 23 are kept at a constant distance from each other in the same attitude, the cylinder head blank 3 is fixed and the spray gun 23 is rotated so that the raw material powder P is sprayed onto the entire circumference of the annular valve seat portion 16c. Fig. 6C is a cross-sectional view showing a state in which the valve seat film 16b is formed on the intake port 16 of Fig. 6B.

[0032] The tip of the nozzle 23d of the spray gun 23 is held by the hand of an industrial robot above the cylinder head 12 fixed to a base. The base or the industrial robot sets the position of the cylinder head 12 or the spray gun 23 so that the central axis Z of the intake port 16 on which the valve seat film 16b is formed is vertical and overlaps with the rotation axis of the spray gun 23. In this state, the spray gun 23 is rotated about the rotation axis while spraying the raw material powder P from the nozzle 23d onto the annular valve seat portion 16c, thereby forming a coating over the entire circumference of the annular valve seat portion 16c.

[0033] During the covering step S3, the nozzle 23d introduces the coolant supplied from the coolant circulation circuit 27 into the flow path from the coolant inlet 23e. The coolant cools the nozzle 23d while flowing from the front end side to the rear end side of the flow path formed inside the nozzle 23d. The coolant that has flowed to the rear end side of the flow path is discharged from the flow path by the coolant outlet 23f and collected.

[0034] When the spray gun 23 completes one rotation around the rotation axis and the formation of the valve seat film 16b is completed, the rotation of the spray gun 23 is temporarily stopped. While the rotation is stopped, the industrial robot to which the spray gun 23 is attached moves the spray gun 23 so that the central axis Z of another intake port 16 where the valve seat film 16b is to be next formed coincides with the reference axis of the industrial robot. Then, after the industrial robot has completed moving the spray gun 23, the rotation of the spray gun 23 is resumed, and the valve seat film 16b is formed in the next intake port 16. By repeating this operation thereafter, the valve seat films 16b, 17b are formed in all the intake ports 16 and exhaust ports 17 of the cylinder head blank 3.

[0035] Returning to FIG. 4, in the finishing process S4, the valve seat films 16b, 17b, the intake port 16, and the exhaust port 17 are finished. In the finishing process of the valve seat films 16b, 17b, the surfaces of the valve seat films 16b, 17b are cut by milling using a ball end mill, and the valve seat film 16b is shaped into a predetermined shape. In the finishing process of the intake port 16, a ball end mill is inserted into the intake port 16 from the opening 16a, and the inner peripheral surface of the intake port 16 on the opening 16a side is cut along the processing line PL shown in FIG. 6D. FIG. 6D is a cross-sectional view showing the intake port on which the valve seat film 16b is formed. The processing line PL is a range in which the excess film SF, which is formed by scattering and adhering the raw material powder P in the intake port 16, is formed relatively thick, more specifically, a range in which the excess film SF is formed thick enough to affect the intake performance of the intake port 16.

[0036] In this way, the finishing step S4 can eliminate the surface roughness of the intake port 16 caused by casting, and can also remove the excess film SF formed in the coating step S3. Fig. 6E is a cross-sectional view showing the intake port 16 after the finishing step of Fig. 4. Note that, like the intake port 16, the exhaust port 17 has a valve seat film 17b formed through the formation of a small diameter portion in the exhaust port 17 by casting, the formation of an annular valve seat portion by cutting, cold spraying of the annular valve seat portion, and finishing. Therefore, a detailed description of the procedure for forming the valve seat film 17b for the exhaust port 17 will be omitted.

[0037] Now, the valve seat of the cylinder head 12 is required to have high heat resistance, wear resistance, and adhesion to withstand the impact from the valve in the combustion chamber 15, and high thermal conductivity for cooling the combustion chamber 15. The raw material powder P used to form the valve seat films 16b, 17b is preferably a metal that is harder than the aluminum alloy for casting that constitutes the cylinder head 12 and that can obtain the heat resistance, wear resistance, adhesion, and thermal conductivity required for the valve seat. Here, in order to increase the wear resistance among the performances required for the valve seat, a hard material may be used for the raw material powder, but if the material is hard, it becomes difficult to plastically deform, and the adhesion to the base material decreases. Conversely, in order to improve the adhesion of the valve seat, a soft material may be used for the raw material powder, but if the material is soft, the wear resistance decreases. Thus, there is a trade-off between wear resistance and adhesion in the cold spray method, and it is difficult to achieve both of these properties.

[0038] Therefore, in the metal film and the method for forming the metal film of the present embodiment, a material containing a soft material and a hard material as main components is used as the raw material powder P by the cold spray method, and the weight ratio of the hard material and the soft material contained in the film is formed so as to differ in the thickness direction of the film and / or the extension direction of the film. That is, the film is formed so that the part requiring adhesion is rich in soft material, while the part requiring wear resistance is rich in hard material. This makes it possible to obtain valve seat films 16b, 17b that are excellent in both wear resistance and adhesion.

[0039] As the soft material of this embodiment, it is preferable to use copper or a copper alloy. As the copper alloy, a precipitation hardened copper alloy can be exemplified. As the precipitation hardened copper alloy, a Corson alloy containing nickel and silicon, a chromium copper containing chromium, a zirconium copper containing zirconium, etc. may be used. Furthermore, for example, a precipitation hardened copper alloy containing nickel, silicon and chromium, a precipitation hardened copper alloy containing nickel, silicon and zirconium, a precipitation hardened alloy containing nickel, silicon, chromium and zirconium, a precipitation hardened copper alloy containing chromium and zirconium, etc. can also be applied. The soft material of this embodiment means a material as a main component whose average hardness is substantially softer than that of a hard material. The soft material of this embodiment is a material whose Vickers hardness when formed alone is less than 500HV, preferably 100 to 400HV.

[0040] The hard material of this embodiment means a material as a main component whose average hardness is substantially harder than the soft material described above. Examples of the hard material of this embodiment include iron or iron-based alloys, cobalt or cobalt-based alloys, chromium or chromium-based alloys, nickel or nickel-based alloys, and molybdenum or molybdenum-based alloys. Examples of the hard material of this embodiment include SKD (die steel), SKH (high-speed steel), and Fe-Mo-Si alloy powder. SKD material, also known as die steel, is a material in which Cr, Mo, and V are added to SK material. The composition of SKD61 material is described in JIS4404, and a representative composition is Fe-0.4C-1.0Si-0.4Mn-5.2Cr-1.3Mo-0.9V (numbers are weight %). Also, there are two types of SKH materials, called high speed steel, a monoglutinous type and a molybdenum type. The composition of SKH51 materials is described in JIS4403, and a representative composition is Fe-0.9C-0.3Si-0.4Mn-4.2Cr-5.0Mo-2.0V-6.5W (numbers are weight %). These hard materials may be used alone or in appropriate combination of two or more types. The hard material of this embodiment is a material with a Vickers hardness of 500HV or more, preferably 600 to 1000HV, when formed alone.

[0041] The metal film of this embodiment is formed so that the weight ratio of the hard material and the soft material contained in the film varies depending on the thickness direction and / or the extension direction of the film. The thickness direction of the film means the up-down direction from the interface with the substrate 4 to the film surface in the cross section of the film. The extension direction of the film means the direction in which the film extends two-dimensionally in a plan view of the film. The metal film 5 of the embodiment shown in FIG. 8 and FIG. 13A to FIG. 13C is an example in which the weight ratio of the hard material and the soft material is changed in the thickness direction of the film, and the metal film 5 of the embodiment shown in FIG. 15 is an example in which the weight ratio of the hard material and the soft material is changed in the extension direction of the film.

[0042] FIG. 8 is a cross-sectional view showing one embodiment of the metal film 5 according to the present invention, and FIGS. 13A to 13C are cross-sectional views showing other embodiments of the metal film 5 according to the present invention and graphs showing the component ratios. In FIG. 8, the metal film 5 such as the valve seat film 16b, 17b is formed on the surface of the substrate 4 such as the cylinder head 12 by the cold spray method. In FIG. 8, the black circles indicate the hard material 52, and the other film portions indicate the soft material 51. In the metal film 5 shown in FIG. 8, the weight ratio of the soft material 51 to the hard material 52 included in the film portion 53 close to the substrate 4 in the thickness direction of the metal film 5 is greater than the weight ratio of the soft material 51 to the hard material 52 included in the film portion 54 far from the substrate 4 in the thickness direction of the metal film 5. In other words, in the embodiment shown in Figure 8, the weight ratio of the soft material 51 and hard material 52 contained in the metal film 5 varies depending on the thickness direction of the film, and in particular, the film portion 53 close to the substrate 4 is made rich in the soft material, and the film portion 54 away from the substrate 4 (in other words, the portion close to the film surface) is made rich in the hard material.

[0043] The metal film 5 of the embodiment shown in FIG. 8 and the metal film 5 of the embodiment shown in FIG. 13A to FIG. 13C are formed by different film forming methods. The metal film 5 shown in FIG. 8 is a film consisting of multiple layers formed by multiple blowing, whereas the metal film shown in FIG. 13A to FIG. 13C is a film consisting of a single layer formed by one blowing. However, in the metal film 5 of the embodiment shown in FIG. 13A to FIG. 13C, the weight ratio of the soft material 51 to the hard material 52 contained in the film portion 53 close to the substrate 4 in the thickness direction of the metal film 5 is greater than the weight ratio of the soft material 51 to the hard material 52 contained in the film portion 54 far from the substrate 4 in the thickness direction of the metal film 5. That is, in the embodiment shown in FIG. 13A to FIG. 13C, the weight ratio of the soft material 51 to the hard material 52 contained in the metal film 5 differs depending on the thickness direction of the film, and the film portion 53 close to the substrate 4 is made soft material rich, and the film portion 54 far from the substrate 4 (in other words, the portion close to the film surface) is made hard material rich.

[0044] FIG. 7 is a graph showing the relationship between the wear resistance and adhesion to the weight ratio of the hard material contained in the metal film formed by the cold spray method. The weight ratio of the hard material 52 refers to a percentage obtained by dividing the weight of the hard material contained in the metal film 5 by the sum of the weight of the hard material 52 and the weight of the soft material 51 contained in the metal film 5. As shown in the figure, when the raw material powder P contains the soft material 51 and the hard material 52, the smaller the weight ratio of the hard material 52, the lower the wear resistance of the metal film 5, and the higher the weight ratio of the hard material 52, the higher the wear resistance of the metal film 5. On the other hand, the larger the weight ratio of the hard material 52, the lower the adhesion to the substrate 4, and the lower the hard material 52, the higher the adhesion of the metal film 5. Strictly speaking, the lower the hard material 52, the higher the adhesion of the metal film 5, and then the lower the adhesion. In other words, when the raw material powder P contains a soft material 51 and a hard material 52, it is understood that the film richer in hard material has better wear resistance but poorer adhesion, and the film richer in soft material has better adhesion but poorer wear resistance.

[0045] In the metal film 5 of the embodiment shown in Fig. 8 and Fig. 13A to Fig. 13C, the film portion 53 close to the substrate 4 is made rich in soft material, and the film portion 54 away from the substrate 4 (in other words, the portion close to the film surface) is made rich in hard material. That is, the film portion 53 close to the substrate 4 that contributes to adhesion to the substrate 4 is made rich in soft material with excellent adhesion, and the film portion 54 close to the surface that contributes to wear resistance due to striking input from the intake valve 18 and the exhaust valve 19 is made rich in hard material with excellent wear resistance. This makes it possible to achieve both wear resistance and adhesion.

[0046] Next, a method of forming a film in which the weight ratio of the hard material and the soft material contained in the film varies depending on the thickness direction and / or the extension direction of the film, as in the metal film 5 of the embodiment shown in Figure 8 and Figures 13A to 13C, will be described. Figures 9A and 9B are plan views showing a procedure for forming the valve seat films 16b, 17b made of the metal film 5 of Figure 8, where Figure 9A shows the case where the lower layer of the valve seat films 16b, 17b is formed, and Figure 9B shows the case where the upper layer of the valve seat films 16b, 17b is formed.

[0047] When metal films 5 such as valve seat films 16b and 17b are formed into a film consisting of multiple layers by overlapping spraying, the weight ratio of hard material to soft material can be controlled by changing the density of raw material powder P during spraying depending on the layer. Fig. 10A is a schematic diagram showing a film formation state when the moving speed of nozzle 23d of cold spray device 2 is low, and Fig. 10B is a schematic diagram showing a film formation state when the moving speed of nozzle 23d is high, showing raw material powder P consisting of soft material 51 and hard material 52. The density of raw material powder P during spraying is determined by the discharge amount of raw material powder P from nozzle 23d and the moving speed of nozzle 23d. Therefore, when the amount of raw material powder P discharged from nozzle 23d is constant, when the moving speed of nozzle 23d is relatively slow, the density (weight per unit volume) of raw material powder P containing a hard material and a soft material during spraying becomes large, as shown in FIG. 10A, and conversely, when the moving speed of nozzle 23d is relatively fast, the density of raw material powder P containing a hard material and a soft material during spraying becomes small, as shown in FIG. 10B.

[0048] Here, the mechanism by which the raw material powder P injected from the nozzle 23d adheres to the surface of the substrate 4 was investigated, and the results are as follows. That is, since the powder of the hard material 52 is harder than the powder of the soft material 51, there is a high probability that the powder of the hard material 52 will bounce back when it collides with the substrate 4. However, as shown in FIG. 10A, if the density of the raw material powder P is high and there is a lot of powder of the soft material 51 around the powder of the hard material 52, the powder of the hard material 52 will be suppressed by the surrounding powder of the soft material 51 even if it tries to bounce back. As a result, the amount of the hard material 52 that does not bounce back and adhere to the substrate 4 is reduced, and the substrate 4 is relatively rich in hard material. On the other hand, as shown in FIG. 10B, if the density of the raw material powder P is low and there is not a lot of powder of the soft material 51 around the powder of the hard material 52, the powder of the hard material 52 will not be suppressed by the surrounding powder of the soft material 51 when it tries to bounce back. As a result, the amount of the hard material 52 that does not bounce back and adhere to the substrate 4 is increased, and the substrate 4 is relatively rich in soft material.

[0049] In this way, when the discharge amount of raw material powder P from the nozzle 23d is constant, when the moving speed of the nozzle 23d is relatively low, the hard material becomes rich as shown in Fig. 10A, and conversely, when the moving speed of the nozzle 23d is relatively high, the soft material becomes rich as shown in Fig. 10B. Therefore, when forming the lower layer of the valve seat film 16b, 17b as shown in Fig. 9A with the discharge amount of raw material powder P from the nozzle 23d constant, the moving speed of the nozzle 23d is set to a relatively high speed V HIGH 9B, when forming the upper layers of the valve seat films 16b and 17b, the moving speed of the nozzle 23d is set to a relatively slow speed V LOW Set to (V HIGH >V LOW ) In this way, the metal film 5 shown in FIG. 8 can be formed.

[0050] As described above, the density of the raw material powder P during spraying is determined by the amount of raw material powder P discharged from the nozzle 23d and the moving speed of the nozzle 23d. When the moving speed of the nozzle 23d is constant, when the amount of raw material powder P discharged from the nozzle 23d is relatively large, the raw material powder P becomes rich in hard material as shown in FIG. 10A. Conversely, when the amount of raw material powder P discharged from the nozzle 23d is relatively small, the raw material powder P becomes rich in soft material as shown in FIG. 10B. Therefore, when the moving speed of the nozzle 23d is constant, the amount of raw material powder P discharged from the nozzle 23d may be set to a relatively small value when forming the lower layer of the valve seat film 16b, 17b as shown in FIG. 9A, and when the upper layer of the valve seat film 16b, 17b as shown in FIG. 9B, the amount of raw material powder P discharged from the nozzle 23d may be set to a relatively large value. This also allows the metal film 5 shown in FIG. 8 to be formed.

[0051] 9A and 9B, a two-layer metal film 5 is formed by two overlapping sprayings, but a three-layer metal film 5 may be formed by three or more overlapping sprayings. In this case, each layer may be set to a different moving speed / discharge amount, or layers with the same moving speed / discharge amount may be included.

[0052] The method of forming the metal film 5 shown in Figures 9A and 9B is a method of forming a metal film 5 consisting of multiple layers by overlapping spraying, but next, a method of forming a metal film 5 consisting of a single layer, such as the metal film 5 shown in Figures 13A to 13C, will be described. Figure 11 is a diagram showing the main configuration of another embodiment of the cold spray apparatus 2 used in this film formation method, and mainly shows the configuration different from the cold spray apparatus 2 shown in Figure 3, with the description of Figure 3 being used for common members. Also, Figure 12 is a side view showing the film formation method using the cold spray apparatus 2 of Figure 11.

[0053] The cold spray device 2 shown in Fig. 11 includes a raw material powder supplying device 221a and a raw material powder supplying line 221c that accommodate a powder of the soft material 51 and supply it to the nozzle 23d, and a raw material powder supplying device 222a and a raw material powder supplying line 222c that accommodate a powder of the hard material 52 and supply it to the nozzle 23d. The two raw material powder supplying lines 221c, 222c join together to form the raw material powder supplying line 22c, which guides the powder of the soft material 51 and the powder of the hard material 52 to the chamber 23a of the nozzle 23d. A partition 22d is provided inside the raw material powder supplying line 22c where the two raw material powder supplying lines 221c, 222c join together, and the powder of the soft material 51 and the powder of the hard material 52 are led to the chamber 23a without being mixed. Incidentally, the provision of partition 22d prevents the powder of soft material 51 and the powder of hard material 52 from mixing until they reach chamber 23a. However, partition 22d may be omitted as necessary, for example, in cases where some mixing is acceptable.

[0054] The powder of the soft material 51 and the powder of the hard material 52 supplied to the chamber 23a of the nozzle 23d are sprayed from the tip of the nozzle 23d while being slightly mixed at the interface between them. At this time, the cone pattern of the sprayed raw material powder P has a pattern in which half P1 contains a large amount of powder of the soft material 51, and the remaining half P2 contains a large amount of powder of the hard material 52, as shown in Fig. 11. Therefore, as shown in Fig. 12, if a metal film is formed in one blow while making the front half P1 of the sprayed raw material powder P in the moving direction X rich in soft material and making the rear half P2 rich in hard material, the lower side of the metal film 5 where the sprayed raw material powder P adheres to the substrate 4 first becomes rich in soft material, and as it is deposited thereon, it becomes rich in hard material.

[0055] FIG. 13A is a cross-sectional view showing the valve seat film 16b, 17b when the metal film 5 is formed as shown in FIG. 12 using the cold spray device 2 shown in FIG. 11, and a graph showing the component ratio. According to this method, the valve seat film 16b, 17b consisting of a single layer can be obtained, in which the film portion 53 close to the substrate 4 is made rich in soft material, and the film portion 54 far from the substrate 4 (in other words, the portion close to the film surface) is made rich in hard material. That is, a single layer film can be formed in which the film portion 53 close to the substrate 4 that contributes to adhesion to the substrate 4 is made rich in soft material with excellent adhesion, and the film portion 54 close to the surface that contributes to wear resistance due to the impact input from the intake valve 18 and the exhaust valve 19 is made rich in hard material with excellent wear resistance. This makes it possible to achieve both wear resistance and adhesion.

[0056] The richness of the hard material and the richness of the soft material in the thickness direction of the metal film 5 are not particularly limited. As shown in the left graph, the metal film 5 of the embodiment shown in FIG. 13A has a component ratio of 0% hard material and 100% soft material at the interface, 100% hard material and 0% soft material at the surface, and changes linearly between them. In contrast, as shown in the left graph, the metal film 5 of the embodiment shown in FIG. 13B has a component ratio of 0% hard material and 100% soft material at the interface, 100% hard material and 0% soft material at the surface, and changes curvedly between them. Also, as shown in the left graph, the metal film 5 of the embodiment shown in FIG. 13C has a component ratio of 25% hard material and 75% soft material at the interface, 90% hard material and 10% soft material at the surface, and changes linearly between them.

[0057] The metal film and the method for forming the metal film of the present invention may be formed so that the weight ratio of the hard material and the soft material contained in the film varies not only in the thickness direction of the film but also in the extending direction of the film. Fig. 14 is a plan view showing valve seat films 16b and 17b of still another embodiment of the metal film 5 according to the present invention. Fig. 14 shows one recess 12b constituting one combustion chamber in a plan view, in which a valve seat film 16b is formed on each of two intake ports 16, and a valve seat film 17b is formed on each of two exhaust ports 17.

[0058] Here, the valve seat films 16b, 17b of this embodiment are configured such that the weight ratio of the hard material to the soft material included in the circumferential portion close to the spark plug SP is greater than the weight ratio of the hard material to the soft material included in the circumferential portion far from the spark plug SP. For example, as shown in the valve seat film 16b in the lower left of Fig. 14, the circumferential portion C2 close to the spark plug SP is made rich in hard material, and the circumferential portion C1 far from the spark plug SP is made rich in soft material. The circumferential portion C2 of the valve seat films 16b, 17b close to the spark plug SP is in a relatively high temperature state compared to the circumferential portion C1 of the valve seat films 16b, 17b far from the spark plug SP, and is subjected to a striking input from the intake valve 18 and the exhaust valve 19, so that the configuration of this embodiment provides higher wear resistance.

[0059] FIG. 15 is a configuration diagram showing yet another embodiment of the cold spray device used in the film forming method according to the present invention, which is a cold spray device 2 used to form the valve seat films 16b and 17b shown in FIG. 14. The configuration upstream of the nozzle 23d is the same as that of the cold spray device 2 shown in FIG. 11, and the description thereof is incorporated herein by reference. The cold spray device 2 of this embodiment differs from the cold spray device 2 of FIG. 11 in that the pattern of the raw material powder P sprayed from the nozzle 23d is doughnut-shaped as shown in the lower diagram of FIG. 15. In addition, the cold spray device 2 of this embodiment does not spray the raw material powder P while rotating the nozzle 23d along the annular valve seat portion 16c as shown in FIG. 6C, but sprays the doughnut-shaped raw material powder P once while facing the intake port 16 or the exhaust port 17 and does not move (the position in the rotation direction is set), thereby forming the valve seat films 16b and 17b. As a result, half P1 of the donut-shaped pattern of the injected raw material powder P becomes a pattern containing a lot of powder of the soft material 51, and the remaining half P2 becomes a pattern containing a lot of powder of the hard material 52, so that the circumferential portion C2 close to the spark plug SP can be made rich in hard material, and the circumferential portion C1 far from the spark plug SP can be made rich in soft material.

[0060] As described above, according to the metal film and the method for forming the same of this embodiment, a metal film having both excellent wear resistance and adhesion can be obtained by making the film portion 53 close to the substrate 4 rich in soft material and making the film portion 54 far from the substrate 4 rich in hard material in the thickness direction of the film.

[0061] Furthermore, according to the metal film and the method for forming the same of the present embodiment, the film is formed so that the weight ratio of the hard material to the soft material varies in the extending direction of the film, thereby making it possible to improve the heat resistance and adhesion in appropriate locations. [Explanation of symbols]

[0062] 1. Internal combustion engine 11...Cylinder block 11a...Cylinder 12...Cylinder head 12a…Mounting surface 12b…Recess 12c,12d…side 13…Piston 13a…Connecting rod 13b…Top surface 14…Crankshaft 15…Combustion chamber 16…Intake port 16a...Opening 16b…Valve seat membrane 16c...Annular valve seat section 17…Exhaust port 17a...Opening 17b…Valve seat membrane 18…Intake valve 18a…Valve stem 18b…Valve head 18c…Valve guide 19…Exhaust valve 19a…Valve stem 19b…Valve head 19c…Valve guide 2…Cold spray device 21…Gas supply section 21a…Compressed gas cylinders 21b…Working gas line 21c…Carrier gas line 21d…Pressure regulator 21e...Flow control valve 21f…Flow meter 21g…Pressure gauge 21h…Power source 21i…Heater 22...Raw material powder supply section 22a,221a,222a...Raw material powder supply device 22b…Measuring instrument 22c, 221c, 222c…Raw powder supply line 22d…Partition 23…Spray gun 23a…Chamber 23b…Pressure gauge 23c…Thermometer 23d…Nozzle 23e…Refrigerant introduction section 23f…Refrigerant discharge part 23g,23h…Signal line 27…Refrigerant circulation circuit 271…Tank 272…Pump 273...Cooler 274...Introduction pipe 275...Discharge pipe 3…Cylinder head raw material 4...Base material 5...Metal film 51…Soft material 52…Hard material SP…Spark plug

Claims

1. A metal film formed on a surface of a substrate, the metal film containing a soft material and a hard material as main components, In a metal film in which the weight ratio of a hard material to a soft material contained in the film varies depending on the thickness direction and / or the extending direction of the film, the metal film constitutes a valve seat of an engine; A metal film in which the weight ratio of the hard material to the soft material included in a circumferential portion closer to the ignition plug is greater than the weight ratio of the hard material to the soft material included in a circumferential portion farther from the ignition plug.

2. 2. The metal film according to claim 1, wherein the weight ratio of the soft material to the hard material contained in the film portion closer to the substrate in the thickness direction of the film is greater than the weight ratio of the soft material to the hard material contained in the film portion farther from the substrate in the thickness direction of the film.

3. 3. The metal film according to claim 1, wherein the soft material is copper or a copper alloy, and the hard material is cobalt, a cobalt alloy, SKD (die steel), SKH (high speed steel), or an Fe-Mo-Si alloy powder.

4. 4. The metal film according to claim 3, wherein the Vickers hardness of the film portion where the weight ratio of the soft material to the hard material contained in the film is relatively large is less than 500 HV, and the Vickers hardness of the film portion where the weight ratio of the soft material to the hard material contained in the film is relatively small is 500 HV or more.

5. A method for forming a metal film by spraying a raw material powder containing a soft material and a hard material as main components onto a surface of a substrate through a nozzle by a cold spray method, comprising the steps of: A method for forming a metal film by changing the density of a raw material powder during injection depending on a portion of the film, comprising: A film forming method in which the moving speed of the nozzle is changed depending on the location while the desired metal film is being formed.

6. The film forming method according to claim 5 , wherein the moving speed when forming a film portion closer to the substrate in the thickness direction of the film is faster than the moving speed when forming a film portion farther from the substrate in the thickness direction of the film.

7. In a case where the base material is a seating portion of an engine valve, and a valve seat made of a plurality of metal films is formed on the seating portion while the nozzle is moved relatively along the seating portion, 7. The film forming method according to claim 5, wherein a moving speed of the nozzle when forming a layer closer to the seating portion is faster than a moving speed of the nozzle when forming a layer farther from the seating portion.

8. A method for forming a metal film by spraying a raw material powder containing a soft material and a hard material onto a surface of a substrate through a nozzle by a cold spray method, comprising the steps of: A film forming method in which the soft material is supplied to a front portion of the inside of the nozzle in the direction of movement and the hard material is supplied to a rear portion, thereby forming a metal film while making the front side of the direction of movement of the sprayed raw material powder rich in soft material and the rear side rich in hard material.

9. 9. The film forming method according to claim 8, wherein the substrate is a seating portion of an engine valve, and a valve seat made of a single-layer metal film is formed on the seating portion while the nozzle is moved relatively along the seating portion.

10. 10. The film forming method according to claim 5, wherein the soft material is copper or a copper alloy, and the hard material is cobalt or a cobalt alloy.

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